A Wild West without vice front-and-center would feel hollow to me. Fortunately Boot Hill doesn't shy away from sin.
BH is pretty frank about the presence of prostitutes in most of its published adventures, which considering the time and the audience is remarkable. 'Saloon girls' are a feature of all the published adventures for BH, but a couple of the modules took the extra step of making sure the referee knew these are whores. The description of the High Pass Hotel in Dead Mule, from BH2 Lost Conquistador Mine, states, "Other special services are available on request, including laudanum and women." Promise City as described in BH3 Ballots & Bullets is equally explicit: the women of the Palace Saloon are described as "crib girls," which is an explicit reference to prostitutes, and the whores at El Parado, the town's cantina, roll their puteros with the connivance of the owner. There is no mention of prices.
The core rules of contain rules for handling drunkenness - in 2e, intoxication lowers Speed and Accuracy while increasing Bravery and, to a limited extent, Strength - an interesting quirk of these rules is, depending on your character's ability scores, it's possible for the increase in Bravery to make your character more accurate, by 'steadying the nerves,' while drunk than he or she is sober. Opiates are called out in the aforementioned adventures as well. As noted above, laudanum is available at the High Pass Hotel in Dead Mule, though once again there's no mention of prices, and the Promise City of Ballots & Bullets includes an opium den where pipes are available for 50¢. The latter states Wang Li's 'cottage' is primarily visited by Chinese, but the town includes only two Chinese families - in our campaign, we took the 'clients are almost invariably Chinese' statement as propaganda by the Wednesday Afternoon Bible Circle and gave the opium den a more vigorous and diverse clientele, which came to include a few player characters as well. Neither adventure provides specific rules for adjudicating opiate use, and it never really seemed necessary in our campaign to create any.
And since I'm on the subject of sex and drugs, I might as well give a shout-out to the rock and roll of its day, the music of Stephen Foster. Inclusive of subjects and themes popular among African-Americans, Foster's melodies are a ubiquitous feature of the period, mostly in the form of sheet music to be performed in the home - before mp3s, before CDs and casettes, before radio, most people made music, and sheet music for private performance was incredibly popular. Now, the blues which are the true precursor to rock and roll are still a couple of decades away in our campaign, but a bunch of drunk and stoned miners and cowhands singing "Hard Times Come Again No More" to a tinny piano or a scratchy fiddle is a staple of setting a scene in our campaign.